Control of seed size by jasmonate.

Seed size, an important agronomic trait determining crop yield, is regulated by multiple plant hormones. Jasmonate (JA) is a key phytohormone required for various plant defenses and diverse developmental processes. Here, we defined an essential role for JA in control of seed size. Through comprehensive analysis of genetic mutants in JA pathway, we showed that seed size was repressed by positive components in JA pathway including COI1, MYC2 (and its homologues), MED25 and JAR1, but promoted by JA signaling repressor JAZ proteins such as JAZ6. We further demonstrated that exogenous application of JA suppressed seed size in a COI1-dependent manner. Our results reveal that JA signaling represses seed size and negatively regulates integument cell proliferation. Elucidation of jasmonate action in seed size control would advance our understanding of inner mechanism of seed size regulation.